Abstract

This work reports on the magnetic interlayer coupling between two amorphous CoFeB layers, separated by a thin Ru spacer. We observe an antiferromagnetic coupling which oscillates as a function of the Ru thickness , with the second antiferromagnetic maximum found for . We have studied the switching of a trilayer for a Ru thickness of and found that the coercivity depends on the net magnetic moment, i.e., the thickness difference of the two CoFeB layers. The antiferromagnetic coupling is almost independent of the annealing temperatures up to while an annealing at reduces the coupling and increases the coercivity, indicating the onset of crystallization. Used as a soft electrode in a magnetic tunnel junction, a high tunneling magnetoresistance of about 50%, a well-defined plateau and a rectangular switching behavior is achieved.

Received 21 April 2004Accepted 13 July 2004Published online 17 September 2004

Acknowledgments:

The authors wish to thank J. Bangert and G. Gieres for fruitful discussions, and H. Mai for experimental support. Financial support of the German Ministry for Education and Research is gratefully acknowledged (Grant 13N8208).